From 6d3d70a72f08cba36c3aef6b59eea8db40eb4071 Mon Sep 17 00:00:00 2001
From: Magento EngCom Team <magento-engcom-team@magento.com>
Date: Tue, 23 Jan 2018 10:56:24 -0600
Subject: [PATCH] :arrow_double_up: Forwardport of magento/magento2#11765 to
 2.3-develop branch

Applied pull request patch https://github.com/magento/magento2/pull/11765.patch (created by @bentideswell) based on commit(s):
  1. 4d79191e6cf75dfde33a6b38a12d9d06c1e1748c
---
 lib/internal/Magento/Framework/View/Layout/etc/elements.xsd | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/internal/Magento/Framework/View/Layout/etc/elements.xsd b/lib/internal/Magento/Framework/View/Layout/etc/elements.xsd
index ea80380865e6a..39cdec05a65ea 100755
--- a/lib/internal/Magento/Framework/View/Layout/etc/elements.xsd
+++ b/lib/internal/Magento/Framework/View/Layout/etc/elements.xsd
@@ -138,7 +138,7 @@
 
     <xs:simpleType name="blockClassType">
         <xs:restriction base="xs:string">
-            <xs:pattern value="[A-Z][a-zA-Z\d]*(\\[A-Z][a-zA-Z\d]*)*"/>
+            <xs:pattern value="[A-Z][_a-zA-Z\d]*(\\[A-Z][_a-zA-Z\d]*)*"/>
         </xs:restriction>
     </xs:simpleType>